1. Field of the Invention
This invention relates generally to microwave and microelectronic apparatus and more particularly to a lowloss waveguide structure located directly over an integrated circuit structure such as a monolithic microwave integrated circuit (MMIC).
2. Description of Related Art
Current integrated circuit designs use either microstrip, stripline or coplanar configurations to interconnect devices and circuit elements. Such lines are also used as a means to provide various passive functions such as filtering. Despite their widespread application, they suffer higher loss and dispersion than a generally rectangular waveguide, particularly at microwave frequencies in the GHz range. This is due to the loss tangent of the substrate material, e.g. gallium arsenide, at such frequencies. Insofar as miniature size waveguides for use above 100 GHz is concerned, fabrication of such structures is conventionally achieved mechanically such as by micromachining. This is not only time consuming, but also costly and difficult to implement particularly where active and passive devices need to be incorporated therewith.